GLES1: Clip plane API and rendering - Add unit tests for the API - Update test expectations + Pass through point size from the vertex array to the shader, required for new tests to pass. BUG=angleproject:2306 Change-Id: Ib19436c1f4cb12873adea94f734c821363f9e27d Reviewed-on: https://chromium-review.googlesource.com/1079993 Commit-Queue: Lingfeng Yang <lfy@google.com> Reviewed-by: Geoff Lang <geofflang@chromium.org>